Electrical heating unit and resistance-coil.



L. W. CAMPBELL.

ELECTRICAL HEATING UNiT AND RESISTANCE COiL.

APPLICATION FILED JUN-I17, 1913.

Patented Apr. F, 1-

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UNITED STATES PATENT OFFICE.

LOUIS WILLIAM CAMPBELL, OF SOUTH YARRA, VICTORIA, AUSTRALIA.

ELECTRICAL HEATING UNIT AND RESISTANCE-COIL.

Application filed June 17, 1913.

T aZZ whom it may concern Be it known that I, LOUIS WVILLIAM CAMP- BELL, a subject of the King of Great Britain, and a resident of 268 Toorak road, South Yarra, in the Stat-e of Victoria, Commonwealth of Australia, have invented certain new and useful Improvements in Electrical Heating Units and Resistance Coils, of which the following is a specification.

The invention relates to electrical resistance devices and, being particularly useful for heating purposes generally, intimately concerns such appliances as radiators, convectors, cooking utensils, soldering irons and the like.

It is well recognized in the art that mica presents a most suitable non-conductor for use in the construction of electrical appliances, but it is also equally well understood that this material is limited in its use owing to its laminated and fragile nature. It is ditficult, for example, to roll a sheet of mica without causing fractures therein. Hitherto mica has generally been used in solid pieces of prismatic formation. This, however, more especially where domestic utensils are concerned, ofiers considerable objections owing to the introduction of undesirable features into the utensils when a heating unit utilizing such mica is employed. The cost is also unduly increased, as also is the space occupied, and the utensils are generally inconvenient to handle. It is a common practice in the art to wind a high resistance wire upon a non-conducting material, and, further, to provide a frame, in some instances, by which the high resistance wire is supported. Often the windings in such latter constructions sag under the influence of heat and come in contact with each other and fuse. Or the corners of the constructions being sharp fracture the oXid covering of the resistance wire causing the said wire to burn out. Or air pockets obtain. Or difficulty is encountered in obtaining and maintaining a perfectly even winding. Still further it is often necessary to employ a meter to ascertain the length of wound wire needed to provide a desired resistance and should mica be employed to support the wire, it has hitherto been impracticable to cut a thread upon the said mica owing to its brittle and delicate nature. Mica has been specified herein because it is a most useful insulating material, and because of the difliculties hitherto encountered in its use, and also for con- Specification of Letters Patent.

Patented Apr. 6, 1915.

Serial No. 774,256.

v venience of description, but it will be appreciated that the invention does not aim at overcoming difliculties inherited by this material only and is not limited thereto.

The main object of this invention is to provide a support for a high resistance wire which will be extremely cheap of manufacture, compact, not liable to rupture and which may be turned, threaded and other wise treated with facility. The invention increases the efliciency and durability of the resistance wire and also provides and insures an even winding thereof upon the support. It also greatly increases the eliiciency and adaptability of appliances with which it is used. The invention, as aforesaid, is particularly adapted to heating units for use with all kinds of commercial and domestic utensils.

The invention primarily consists in mounting a series of washers (which may be formed from waste mica or other material) upon a supporting rod and compressmg them into a solid mass. This may be assisted by heating the mass and hammermg or likewise treating its periphery after compression. An adhesive or binding material may also be used. A thread or spiral groove may then be cut with facility upon the support thus formed and a high resist ance wire or coil be placd in the thread or groove. By means of the thread, not only is the high resistance wire always in contact with the insulating material, thereby avoiding burn outs and fusings, but the length of the wire wound is accurately measured and known by the length of the thread, the necessity of meters to indicate the resistance being thereby rendered unnecessary. After winding the resistance wire in the thread, the periphery of the support is preferably rolled or compressed laterally by rollers or the like, thereby overturning the outer edge of the thread and embedding the resistance wire in the support. But in order that this invention may be better understood, reference will now be made to the accompanying sheet of drawings, which are to be taken as part of this specification and read herewith.

Figure 1 is a view of a supporting rod having a tubular support threaded to one end thereof. Portion has been broken away for convenience of illustration. Fig. 2 is a sectional view of a tubular supporting rod. Portion has been broken away for convenience of illustration. Fig. 3 is a view of a mica or other washer. Fig. 4 is a view showing a series of mica or other washers forming an insulator and retained upon the sup porting rod by nuts thereon. Fig. 5 is a sectional end view taken on line AA, Fig. 6. Fig. 6 is a view of an insulator formed from mica or other washers and having a threaded periphery. Portion is shown in section for convenience of illustration. Fig. 7 is a cross section of an insulator having a return hole therethrough. Fig. 8 is a plan of Fig. 6. Fig. 9 is a sectional view of a terminal consisting of a nipple and plug threaded to the supporting rod. Fig. 10 is a part sectional view of a modification of Fig. 9. Fig. 11 is a view of a sleeve showing transverse slotways therein. Fig. 12 is a plan of Fig. 11. Fig. 13 is a cross section of the sleeve taken on line B-B, Fig. 11. Fig. 14 is a perspective View of a retention band. Fig. 15 is a plan view of a modified terminal. Fig. 16 is a part sectional view of a resistance device or heating unit, according to the invention. Fig. 17 is a perspective view showing a lining and casing which may be used with the unit; Fig. 18 is a part sectional view showing a lining and casing in position around the unit. Fig. 19 is a perspective View, on a reduced scale, of a modified unit. Fig. 20 is a detail view showing portion of a support having a resistance wire embedded therein.

The invention includes a metallic supporting rod 2, having a right threaded end 3 and a left threaded end 4. The rod may be solid, as seen in Fig. 1, or it may be tubular, as seen in Fig. 2. In the latter instance it is provided with a central longitudinal passageway 5. Mounted upon the right end 3, is a right metallic or other washer 6. Mounted upon the left end 4, is a left metallic or other washer 7 Formed through the right washer 6, is a resistance wire hole 8. Retaining the washers 6 and 7 upon the supporting rod are nuts 9. Threaded upon the right end 3, may be a tubular or like support 10, which may act as a bearing or rest, if employed.

Mounted upon the supporting rod 2, and compressed between the washers 6 and 7 by end pressure exerted by the nuts 9, is a series of mica or other washers 11, each having a central hole 12 therein. An adhesive may also be used to retain the washers together. The compressed washers 11 form an insulator. Formed through the insulator may be a return lead hole 13. The surface of the insulator formed by the washers 11 is often (more or less) uneven and to provide a smooth periphery it is heated and then hammered, rolled, swaged or otherwise treated. It is then finished in a lathe or the like by suitable cutting tools; or it is filed or otherwise treated to smooth the periphery.

Formed upon the smooth periphery is a spiral groove or thread 14. This may be of any desired angle or pitch. Orinstead of a single thread, a series of threads may be cut thereon. Passing from the left end of the insulator to the corresponding end of the thread 14 is an oblique wire path 15. Formed through the right end of the insulator, and communicating with the corresponding end of the thread 14, is a tangential or oblique hole 16. Integral with the left end of the insulator is a reduced extension 17, having a shoulder 18. Formed in the extension 17 are two (more or less) transverse grooves, flats, or recesses 19.

lVith the foregoing is used a nipple 20, having an internal thread engaging the left threaded end 4 of the supporting rod 2. Mounted upon the nipple is a distance collar 21 formed from mica washers in the manner described. Threaded into the nipple 20 is the threaded end 22 of a terminal plug. This is also provided with a bifurcated end 23.

Instead of the terminal plug described, a plug may be used consisting of a socket 24, having an internal thread engaging the left threaded end 4 of the rod 2. Integral with the socket 24 is a bifurcated end 25.

Mounted upon the reduced extension 17 is a metallic sleeve, having an open inner end 26 and an open outer end 27. Formed in the inner end 26 are slotways 28 and 29.

The slotways correspond with the grooves 19. The sleeve instead of being open at its outer end may be closed, as seen in Fig. 15. It is then provided with an integral fiat extension 30, having a wire or terminal screw hole 31. \Vhen a sleeve having a closed outer end is used the terminal plug is dispensed with, as will be hereinafter understood.

With the sleeve is used a metallic retention band 32, having an enlarged end 33 provided with a tongueway 34 through which passes a tongue 35. In use the tongue 35 is passed through the tongueway 34 and then overturned or clenched. The band is disposed in the slotways 28 and 29 and grooves 19. It thereby retains the sleeve upon the reduced eXtention 17. /Vound upon the periphery of the insulator is a high resistance wire 36, having a right end 37 and a left end 38. The left end 38 is disposed in the oblique path 15 and is fused or otherwise secured to the band 32. The band 32, therefore, in addition to retaining the sleeve aforedescribed, also provides a terminal for one end of the high resistance wire. The resistance wire is accommodated in the spiral groove or thread 14, the coils formed being thereby prevented from becoming displaced and being completely insulated from each other. The right end 37 of the wire passes through the tangential or oblique hole 16 and through the hole 8 in the right washer 6, being fused or otherwise secured thereto. The washer 6, therefore, provides a terminal for the other end of the high resistance wire.

After the resistance wire 36 has been placed in position upon the support, the periphery of the insulator may be subjected to lateral pressure by rollers or the like. The outer edges of the spirals of the thread are thereby compressed, expanded, or overturned into the grooves thereof, embedding the high resistance wire in the insulator, as shown in Fig. 20.

Then used for some purposes, such as in connection with soldering and smoothing irons and hot plates, the unit may be enveloped by a mica or other suitable lining 39. This may be inclosed within a metallic or other casing 40.

As shown in Fig. 19, a series of parallel high resistance wires 36 may be used, and, if desired, the washers 11 may be elongated and supported by a plurality of rods 2, a

' rod being provided for each wire, but it will be readily appreciated that the insulator may, if desired, be round in cross section, and that a single rod only need be employed for all of the Wires.

lVith this invention the current leading in wire is secured to the outer end 27 of the sleeve in any well-known way, such as by a concentric sleeve. The current return wire is secured to the bifurcated end 23 of the terminal plug by similar or any other suitable means. The current passes through the sleeve to the left end 38 of the resistance wire and passes through the same to the right end 37. It passes through the washer 6, through the supporting rod 2 to the terminal plug carried by the said rod. It will thus be seen that the supporting rod 2 forms a return lead.

Should a sleeve having a closed outer end be used, the terminal plug is dispensed with and the supporting rod not used as a return lead. The supply wire completing the circuit may then be secured to the right hand end of the device in any suitable manner. Or two sleeves each having a closed outer end may be used, one at each end of the device.

In some circumstances the return lead may be taken through the hole 13 instead of through the supporting rod 2, or it may be taken away from the right hand end of the device.

Should a tubular supporting rod 2 be employed, it may be of any cross section, and supply and delivery pipes may communicate with the ends thereof in any suitable manner for the purpose of heating air, liquid, or other fluids which may circulate or pass through the said tubular rod. IVhen employing a tubular supporting rod, sleeves and concentric plugs or the like may be used as terminals. If desired, the return lead could be taken through the passageway 5 of the said rod.

In practice it has been found that with a unit constructed as described heat is conducted readily and uniformly and that an insulator constructed of mica washers as described, when subjected to great heat, becomes a solid bar possessing considerable durability.

Various details of construction may obviously be modified without departing from the spirit and scope of the invention, the novel features of which are pointed out in the appended claims.

Having now fully described and ascertained my said invention and the manner in which it is to be performed, I declare that what I claim is 1. As an article of manufacture an insulator consisting of a series of mica disks having their edges percussively united and hardened.

2. As an article of manufacture, an insulating member consisting of a series of mica washers compressed together and having their edges percussively united and hard ened.

3. In a device of the kind described, a supporting rod, a series of mica washers mounted on said rod, and means carried by the rod for compressing the washers thereon said washers having their edges percussively united and hardened.

4. Improvements in electrical heating units and resistance coils, consisting in a supporting rod, a series of washers carried by said rod, means for compressing said washers, and a terminal supported at one end of said rod and insulated therefrom.

5. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of washers mounted upon said rod, means for compressing said washers, a reduced extension at one end of said washers, and a terminal mounted upon said extension.

6. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of washers mounted upon said rod, means for compressing said wash ers longitudinally, a terminal sleeve mounted upon one end of the washers, and a terminal plug mounted upon the corresponding end of the supporting rod.

7. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of mica washers mounted upon said rod, nuts mounted upon said rod and compressing said washers, a reduced extension at one end of said washers,a sleeve mounted upon said extension, and a terniinal plug mounted upon the corresponding end of the supporting rod.

8. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of Washers mounted upon said rod, nuts mounted upon said rod and compressing said Washers, a reduced extension at one end of said Washers, said extension having grooves formed therein, a sleeve mounted upon said extension, said sleeve having grooves formed therein, a retention band passing around said sleeve and through said grooves, and a terminal plug mounted upon the corresponding end of the supporting rod.

9. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of Washers mounted upon said rod, metallic Washers mounted upon said rod at each end thereof, nuts mounted upon said rod and compressing the Washers, a reduced extension at one end of the mica Washers, said extension having grooves therein, said Washers forming an insulator, said insulator having a thread or spiral groove formed upon its periphery, a sleeve mounted upon the reduced extension, said sleeve having grooves therein, a retention band passing around said sleeve and through said grooves, and a terminal plug mounted upon the corresponding end of the supporting rod; 7

10. Improvements in electrical heating units and resistance coils, consisting in a supporting rod, a series of Washers mounted upon said rod and forming an insulator, nuts mounted upon said rod and compressing said Washers, said insulator havinga spirally grooved or threaded periphery, a reduced extension at one end of said insulator, said insulator having a tangential hole formed through its other end, said extension having grooves therein, a sleeve mounted upon said extension, said sleeve having grooves therein, a retention band passing around said sleeve and passing through said grooves, a terminal plug mounted upon the corresponding end of the supporting rod Within said sleeve, and a distance collar situated between said plug and the interior of the sleeve.

11. Improvements in electrical heating units and resistance coils consisting in a sup porting rod, nuts mounted upon said rod, a se'ies of Washers mounted upon said rod Copies and compressed by said nuts and forming an insulator, said insulator having a threaded periphery, said insuluator having an oblique Wire path at one end of the thread and a tangential hole at the other, a reduced extension adjoining the oblique path, said extension having grooves therein, a sleeve upon said extension, said sleeve having grooves therein, a retention band passing around said sleeve and through said groove, said band having a tongueway therein, a nipple threaded to the corresponding end of the supporting rod Within the sleeve, a distance collar mounted upon said nipple, a terminal plug threaded to said nipple, and a tubular support threaded to the other end of the supporting rod.

12. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of mica Washers mounted upon said rod, means for compressing said washers, said Washers forming an insulator, a terminal sleeve having a closed outer end mounted upon one end of said insulator, and a flat extension projecting from said closed outer end.

18. Improvements in electrical heating units and resistance coils consisting in a supporting rod, a series of mica Washers mounted upon said rod, means for compressing said Washers, said Washers forming an insulator, said insulator having a threaded periphery, a reduced extension at one end of said insulator, a terminal sleeve having a closed outer end mounted upon said extension, a flat extension projecting from said closed outer end, and a retention band passing around said sleeve.

1%. In a resistance unit, the combination of a rod, mica Washers strung on said rod to form an insulating body having a cylindrical exterior surface, and heads on said rod holding said Washers compressed tightly between them, said body having a helical groove in its peripheral surface.

Dated this 19th day of April, A. D. 1913.

In testimony whereof I aflix my signature in presence of two Witnesses.

LQUIS NILLIAIVI CAMPBELL.

Witnesses:

A. J. CALLINAN, Janus H. ANDERSON.

of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, 110. 

